Avestan (uves'tun) [key], language belonging to the Iranian group of the Indo-Iranian subfamily of the Indo-European family of languages. One of the earliest forms of the Iranian languages to survive, Avestan is also the tongue of the Avesta, or scriptures of Zoroastrianism. See Indo-Iranianlanguages.
See A. V. W. Jackson, An Avestan Grammar in Comparison with Sanskrit (1968).